Obesity is a major and growing health problem worldwide. It is associated with many life-threatening diseases such as cardiovascular disease, renal disease, hypertension, stroke, infertility, respiratory dysfunction, and type 2 diabetes.
Glucagon and glucagon-like peptide-1 (GLP-1) derive from pre-proglucagon, a 158 amino acid precursor polypeptide that is processed in different tissues to form a number of different proglucagon-derived peptides, including glucagon, glucagon-like peptide-1 (GLP-1), glucagon-like peptide-2 (GLP-2) and oxyntomodulin (OXM), that are involved in a wide variety of physiological functions, including glucose homeostasis, insulin secretion, gastric emptying, and intestinal growth, as well as the regulation of food intake. Glucagon is a 29-amino acid peptide that corresponds to amino acids 33 through 61 of proglucagon (53 to 81 of preproglucagon), while GLP-1 is produced as a 37-amino acid peptide that corresponds to amino acids 72 through 108 of proglucagon (92 to 128 of preproglucagon). GLP-1(7-36) amide or GLP-1(7-37) acid are biologically active forms of GLP-1, that demonstrate essentially equivalent activity at the GLP-1 receptor.
Glucagon is produced by the pancreas and interacts with the glucagon receptor (“glucR”). Glucagon acts in the liver to raise blood glucose via gluconeogenesis and glycogenolysis. When blood glucose begins to fall, glucagon signals the liver to break down glycogen and release glucose, causing blood glucose levels to rise toward a normal level.
GLP-1 has different biological activities compared to glucagon. It is secreted from gut L cells and binds to the GLP-1 receptor. Its activities include stimulation of insulin synthesis and secretion, inhibition of glucagon secretion, and inhibition of food intake.
Both glucagon and GLP-1, acting as agonists at their respective receptors, have been shown to be effective in weight loss. Certain GLP-1 analogs are being sold or are in development for treatment of obesity including, e.g., Liraglutide (VICTOZA® from Novo Nordisk) and Exenatide (Byetta® from Eli Lilly/Amylin). Glucagon/GLP-1 agonist peptides have also been disclosed in WO 2014/091316.
While some therapies are available for the control of blood glucose, none currently achieve substantial weight loss, which remains a significant unmet need for patients. Fifty percent of patients progress from oral monotherapy for glucose control (usually with metformin) to initiation of insulin within 10 years, often taking multiple oral combination therapies before initiating insulin. The use of insulin exacerbates weight gain, which can be as great as 6 kg in the first year after starting insulin therapy. This weight gain can lead to increased insulin resistance, which is associated with hypertension, dyslipidemia, and an increased risk of major adverse cardiovascular events. With respect to reducing insulin resistance, significant weight loss (>5%) is the optimal intervention to reduce insulin resistance, although this can only be achieved reliably at present through intensive dietary and lifestyle interventions and/or bariatric surgery. There remains a need for methods of administering GLP-1/Glucagon agonist peptides to humans using dosage regimens that are therapeutically effective in treating diabetes and obesity but avoid adverse effects.